The suggestion and realization for reducing the size of an alphabet keyboard have been continuously performed. Korean Patent Publication No. 10-2001-0025429 (published on Apr. 6, 2001; METHOD FOR INPUTTING ENGLISH USING THE COMPACT KEY-PAD) suggests a compact key-pad that inputs a character key and a function key by simultaneously pressing these keys.
The type of a representative compact alphabet character input device similar to the related art and the problems thereof are described as follows.
FIG. 1 is a diagram showing an arrangement structure of an existing alphabet input device that uses a toggle type. Referring to FIG. 1, in a general input system having a 4×3 key structure, since the characters are dependently arranged irrespective of the frequency in use of the alphabets, there is an inconvenience that the input is performed up to 4 times in order to input one character dependent on each representative character.
When two characters included in the same character or the same key are successively input, since a delimiter is separately input, the typing count is up to 6 times, and thus, the typing count is wasted. Accordingly, there is a limitation in performing high-speed input in the compact device.
FIG. 2 is a diagram showing an arrangement structure of a one-to-one input type QWERTY technology. In such an input type, a compact mechanical input device having a structure in which independent keys are respectively input and physical touch is used. However, since the weight and size of a handheld device are remarkably affected by the arrangement of the input system, the portability of the handheld device is deteriorated.
A touch-type QWERTY input device in which independent keys are input on a screen display device (LCD display etc.) is used as another method. However, since the size of an input unit is reduced, there is a problem that a typographical error rate is increased, and since there is a limitation of the size capable of being minimized, such a input device is unsuitable for universally being used in all compact devices.
FIGS. 3 and 4 are diagrams showing character input arrangement structures using the combination method of the related art. In the method shown in FIGS. 3 and 4, in order to achieve the minimum typing count and the combination principle, the representative keys are arranged in consideration of the frequency of use, and thus, an input speed is partially enhanced. However, there may be a discrepancy in interpretation of a combination form between individuals.
Since there is little correlation between combinations in many cases, a user is difficult to learn the usage, and since it takes a long time to learn the usage, there is a limitation of practical values.
Even though there are various alphabet input methods, a general and ultimate compact alternative input system does not come into wide use.